Technical Field
This disclosure relates to circuits. More specifically, this disclosure relates to a phase noise measurement and filtering circuit.
Related Art
Phase noise limits the performance of many systems, such as communication systems, imaging systems, sensing systems, and radar systems. To suppress phase noise, feedback and feed forward noise cancellation have been investigated. For example, see (1) A. Imani and H. Hashemi, “A Low-Noise FBAR-CMOS Frequency/Phase Discriminator for Phase Noise Measurement and Cancellation”, in Proc. IEEE RFIC Symp, 2013 (hereinafter “Imani”), (2) S. Min, T. Copani, S. Kiaei, and B. Bakkaloglu, “A 90 nm CMOS 5 GHz Ring Oscillator PLL with Delay-Discriminator Based Active Phase Noise Cancellation”, in Proc. IEEE RFIC Symp, 2012 (hereinafter “Min”), and (3) W. Khalil, B. Bakkaloglu, and S. Kiaei, “A Self-Calibrated On-Chip Phase-Noise-Measurement Circuit With −75 dBc Single-Tone Sensitivity at 100 kHz Offset”, IEEE J. Solid-State Circuits, vol. 41, no. 12, pp. 2758-2765, 2007 (hereinafter “Khalil”).
The capability of existing phase noise cancellation systems is limited by the phase noise measurement (PNM) circuit noise floor, which determines the best achievable phase noise performance. A delay line with large delay time and low phase noise is an important component of PNM. The approach in Imani adopts a high-Q FBAR filter as delay line to extract phase noise, which demonstrates a noise sensitivity of −162 dBc/Hz at 1 MHz offset. However, the operational bandwidth of this approach is limited by the high-Q filter, which is very small. The approaches in Min and Khalil utilize an active delay line chain to extract the phase noise, which is constrained by the high noise contribution from the active delay line itself.
Moreover, the PNM accuracy of existing approaches are vulnerable to environment noises, such as cross-talk and coupling noise. This drawback impedes the integration of the PNM into larger systems, where other circuits/sub-systems may produce a variety of coupling spurs and noises. Therefore, what are needed are PNM circuits without the above-described drawbacks.